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Signed-off-by: Andrej Orsula <orsula.andrej@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,5 @@ | ||
| Register A: 56256477 | ||
| Register B: 0 | ||
| Register C: 0 | ||
|
|
||
| Program: 2,4,1,1,7,5,1,5,0,3,4,3,5,5,3,0 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,197 @@ | ||
| use aoc_runner_derive::aoc; | ||
| use itertools::Itertools; | ||
|
|
||
| #[aoc(day17, part1)] | ||
| #[must_use] | ||
| pub fn part1(input: &str) -> String { | ||
| let mut prog = Program::parse(input); | ||
| std::iter::from_fn(|| prog.step()).join(",") | ||
| } | ||
|
|
||
| #[aoc(day17, part2)] | ||
| #[must_use] | ||
| pub fn part2(input: &str) -> usize { | ||
| Program::parse_instructions(input, 0) | ||
| .instructions | ||
| .into_iter() | ||
| .rev() | ||
| .fold( | ||
| smallvec::SmallVec::<[usize; 32]>::from_elem(0, 1), | ||
| |queue, instruction| { | ||
| queue | ||
| .into_iter() | ||
| .flat_map(move |i| { | ||
| (0..8).filter_map(move |j| { | ||
| let reg_a = j | (i << 3); | ||
| Program::parse_instructions(input, reg_a) | ||
| .step() | ||
| .is_some_and(|i| i == instruction as usize) | ||
| .then_some(reg_a) | ||
| }) | ||
| }) | ||
| .collect() | ||
| }, | ||
| )[0] | ||
| } | ||
|
|
||
| #[derive(Debug)] | ||
| struct Program { | ||
| instructions: smallvec::SmallVec<[u8; 16]>, | ||
| reg_a: usize, | ||
| reg_b: usize, | ||
| reg_c: usize, | ||
| pointer: usize, | ||
| } | ||
|
|
||
| impl Program { | ||
| #[inline] | ||
| fn parse(input: &str) -> Program { | ||
| let (registers, instructions) = unsafe { input.split_once("\n\n").unwrap_unchecked() }; | ||
| let reg_a = registers | ||
| .bytes() | ||
| .skip(12) | ||
| .take_while(u8::is_ascii_digit) | ||
| .fold(0, |num, b| unsafe { | ||
| 10_usize | ||
| .unchecked_mul(num) | ||
| .unchecked_add(b.unchecked_sub(b'0') as usize) | ||
| }); | ||
| let instructions = instructions | ||
| .bytes() | ||
| .skip(9) | ||
| .step_by(2) | ||
| .map(|b| unsafe { b.unchecked_sub(b'0') }) | ||
| .collect(); | ||
|
|
||
| Self { | ||
| instructions, | ||
| reg_a, | ||
| reg_b: 0, | ||
| reg_c: 0, | ||
| pointer: 0, | ||
| } | ||
| } | ||
|
|
||
| #[inline] | ||
| fn parse_instructions(input: &str, reg_a: usize) -> Program { | ||
| let (_, instructions) = unsafe { input.split_once("\n\n").unwrap_unchecked() }; | ||
| let instructions = instructions | ||
| .bytes() | ||
| .skip(9) | ||
| .step_by(2) | ||
| .map(|b| unsafe { b.unchecked_sub(b'0') }) | ||
| .collect(); | ||
|
|
||
| Self { | ||
| instructions, | ||
| reg_a, | ||
| reg_b: 0, | ||
| reg_c: 0, | ||
| pointer: 0, | ||
| } | ||
| } | ||
|
|
||
| #[inline] | ||
| fn step(&mut self) -> Option<usize> { | ||
| while self.pointer < self.instructions.len() { | ||
| match self.instructions[self.pointer] { | ||
| 0 => { | ||
| self.reg_a >>= match self.instructions[unsafe { self.pointer.unchecked_add(1) }] | ||
| { | ||
| instruction @ 0..4 => instruction as usize, | ||
| 4 => self.reg_a, | ||
| 5 => self.reg_b, | ||
| 6 => self.reg_c, | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } | ||
| } | ||
| 1 => { | ||
| self.reg_b ^= | ||
| self.instructions[unsafe { self.pointer.unchecked_add(1) }] as usize; | ||
| } | ||
| 2 => { | ||
| self.reg_b = match self.instructions[unsafe { self.pointer.unchecked_add(1) }] { | ||
| instruction @ 0..4 => instruction as usize, | ||
| 4 => self.reg_a, | ||
| 5 => self.reg_b, | ||
| 6 => self.reg_c, | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } % 8; | ||
| } | ||
| 3 => { | ||
| if self.reg_a != 0 { | ||
| self.pointer = | ||
| self.instructions[unsafe { self.pointer.unchecked_add(1) }] as usize; | ||
| continue; | ||
| } | ||
| } | ||
| 4 => self.reg_b ^= self.reg_c, | ||
| 5 => { | ||
| let i = match self.instructions[unsafe { self.pointer.unchecked_add(1) }] { | ||
| instruction @ 0..4 => instruction as usize, | ||
| 4 => self.reg_a, | ||
| 5 => self.reg_b, | ||
| 6 => self.reg_c, | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } % 8; | ||
| self.pointer = unsafe { self.pointer.unchecked_add(2) }; | ||
| return Some(i); | ||
| } | ||
| 6 => { | ||
| self.reg_b = self.reg_a | ||
| >> match self.instructions[unsafe { self.pointer.unchecked_add(1) }] { | ||
| instruction @ 0..4 => instruction as usize, | ||
| 4 => self.reg_a, | ||
| 5 => self.reg_b, | ||
| 6 => self.reg_c, | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } | ||
| } | ||
| 7 => { | ||
| self.reg_c = self.reg_a | ||
| >> match self.instructions[unsafe { self.pointer.unchecked_add(1) }] { | ||
| instruction @ 0..4 => instruction as usize, | ||
| 4 => self.reg_a, | ||
| 5 => self.reg_b, | ||
| 6 => self.reg_c, | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } | ||
| } | ||
| _ => unsafe { std::hint::unreachable_unchecked() }, | ||
| } | ||
| self.pointer = unsafe { self.pointer.unchecked_add(2) }; | ||
| } | ||
| None | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use indoc::indoc; | ||
|
|
||
| const SAMPLE1: &str = indoc! {" | ||
| Register A: 729 | ||
| Register B: 0 | ||
| Register C: 0 | ||
| Program: 0,1,5,4,3,0 | ||
| "}; | ||
| const SAMPLE2: &str = indoc! {" | ||
| Register A: 2024 | ||
| Register B: 0 | ||
| Register C: 0 | ||
| Program: 0,3,5,4,3,0 | ||
| "}; | ||
|
|
||
| #[test] | ||
| pub fn part1_example() { | ||
| assert_eq!(part1(SAMPLE1), "4,6,3,5,6,3,5,2,1,0"); | ||
| } | ||
|
|
||
| #[test] | ||
| pub fn part2_example() { | ||
| assert_eq!(part2(SAMPLE2), 117_440); | ||
| } | ||
| } |
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